A variety of complications involving the oral cavity may be seen in cancer patients either as a result of the disease itself or of treatment with chemotherapeutic agents. In chemotherapy, most complications are the result of myelosuppression, immunosuppression, and direct cytotoxic effects on oral tissues. Chemotherapy may also adversely affect the salivary glands resulting in an alteration of the quality and quantity of saliva. In a recent study from our laboratory we analyzed saliva samples from 25 leukemia patients undergoing chemotherapy and found that there is very little change in the concentrations of proteinaceous components of saliva. However, analysis of our data revealed that the concentration of thiocyanate (SCN-) in saliva of these patients is reduced significantly and that this reduction is correlated to a simultaneous reduction in the number of granulocytes. These observations imply that the decrease in the SCN- concentration impairs the normal function of the salivary peroxidase (SP) system and this in turn leads to high concentrations of hydrogen peroxide which may be deleterious to the oral mucosa. The biological significance of the SP system would be apparent if one could find a population deficient in this enzyme, however, to date no such patients have been identified. Our recent study of leukemia patients undergoing chemotherapy has identified a population which is deficient in one of the components of the SP system, namely SCN-. In order to determine if the changes of this system are related to the disease itself or to the treatment, and to better understand the protective role of the SP system in oral health, we propose to study the system components in cancer patients undergoing chemotherapy. We will also determine the concentrations of SCN- and CN- in the serum of these patients hoping to elucidate some of the mechanisms involved in SCN- metabolism in the salivary glands. We will analyze the same factors in saliva and serum of healthy control subjects. The data will be analyzed statistically and relationships between the changes in SP components and other parameters will be sought.